+xYou've got nothing to worry about with your caution.
So how would that work with the actual question asked on ETA?
"Have you ever committed, been arrested for, been charged with or convicted of any criminal offence in any country?"
'Select ‘Yes’ if you have ever committed, been charged with or convicted of a crime in any country. Please provide as many details as possible. Failure to include additional and sufficient details may result in slower processing.'
Unlike the question on ESTA, where you can tick 'no' for some crimes, the Canadian question doesn't seem to have a get-out, even if you are rehabilitated.